Orientation tracking systems are used to track the position and orientation of a person, a part of a person, e.g., the head, or an object. A few conventional uses of orientation tracking systems include flight simulators and immersive training simulators, such as medical driving simulators.
One key orientation tracking system is a head orientation tracking system for flight deck personnel. These systems typically track the position and orientation of a subject on the flight deck of an aircraft carrier or airfield. This may be of considerable importance when a clear line of sight of the person or clear GPS link cannot be assured. The head orientation tracking system may also be used to return directional sound queues to the flight deck personnel to orient them when hearing protection is being used. For example, a head orientation tracking system may provide sound queues regarding incoming flights at a time when flight deck personnel may not be able to hear them due to the hearing protection needed for the high sound levels.
Conventional head orientation tracking systems may not be appropriate for use on a flight deck. For example, one conventional head tracking system relies on using magnets which may not operate adequately in the very high electromagnetic environment of a flight deck. Other conventional head orientation tracking system relies on ultrasonic or IR technologies. Such a system may require a direct line of sight. Video tracking head orientation tracking systems are also not desirable because they can be bulky and operate slowly. Other conventional head orientation tracking system may rely on the use of an inertial mass MEMS sensor. Such a system may be subject to stochastic noise that, when integrated twice to determine position, may create considerable drift which over time will provide an inaccurate reading of location.
Inclinometers, which can be used to determine orientation in one direction, are relatively known in the art. Liquid with a gas bubble is used in standard inclinometers such as levels found at most hardware stores. U.S. Pat. No. 4,587,741 discloses an inclinometer having a toroidal race containing a spherical ball free to move therein under the influence of gravity. Multiple such inclinometers can also be implemented in a system. However, the inclinometer disclosed in the '741 patent uses electrodes to sense the position of the ball. Such an inclinometer may not work adequately in environments which are exposed to high electromagnetic fields. U.S. Pat. Nos. 5,645,077, 5,807,284, 6,162,191, and 6,786,877 B2 each disclose an inertial orientation tracker with automatic drift compensation. Each of these systems, however, is large and relies on a mechanical design.